1. Field of the Invention
The present invention relates to a display apparatus for displaying an image based, for example, on a video signal such as liquid crystal projector and a driving method of the same.
2. Description of the Related Art
A liquid crystal projector is a projector apparatus using spatial light modulators (hereinafter referred to as liquid crystal panels) which include a liquid crystal material. The liquid crystal panels of a liquid crystal projector do not emit light themselves.
In a liquid crystal projector, therefore, the liquid crystal panels are used in combination with a light source to irradiate light, thus illuminating the panels.
Then video signals are applied to the liquid crystal panels. The images formed by the liquid crystal panels are projected onto the screen by a projection lens.
A liquid crystal projector configured as described above can provide a compact and highly efficient projector apparatus.
Incidentally, some liquid crystal materials have the property to change the polarization of an incident beam (polarimetric property) according to the electric field applied. Many liquid crystal panels take advantage of this property to perform optical modulation. Therefore, a polarizing plate has to be provided on the incident side of the liquid crystal panel so that a unidirectional linear polarization (p- or s-polarization) is incident on the panel. A beam emerges from the liquid crystal panel after having undergone rotation of its polarization direction according to a video signal applied to the panel. A modulated beam based on the video signal can be obtained by allowing the polarization in a specific direction to pass through a polarizing plate. Therefore, a polarizing plate is provided as an analyzer on the emergent side of the liquid crystal panel for optical modulation.
On the other hand, a projector has been proposed which has the aperture on/off mode switching function so as to provide an easy-to-see display screen according to the environmental conditions in which the screen is installed. Further, a projector has been proposed which automatically controls the aperture opening diameter (refer, for example, to Japanese Patent Laid-Open No. 2006-133750).